Synthesis and Applications of Non-migratory Metal Chelating Active Packaging

Many packaged foods use synthetic chelators (e.g. ethylenediaminetetraacetic acid, EDTA) to inhibit metal promoted oxidation and/or microbial growth that may cause food spoilage. Consumer demand for foods without synthetic additives has prompted growing interest in alternative preservation methods. Our research group has previously developed non-migratory metal chelating active packaging materials by surface immobilization of polymeric chelators and demonstrated their ability to inhibit lipid oxidation in model food emulsions. The work presented in this dissertation investigates the synthesis, performance stability, and practical application of metal chelating surface modifications to optimize design of non-migratory metal chelating active packaging materials. Metal chelating active packaging materials were synthesized by grafting of metal chelating polymers from the surface of polypropylene (PP). Three metal chelating ligand chemistries were investigated for their known affinity for iron: carboxylic acids, hydroxamic acids, and catechols. Iron was chosen a target metal ion because it is a strong prooxidant and essential nutrient for spoilage bacteria. When utilizing photoinitiated graft polymerization to surface graft poly(acrylic acid) that contained carboxylic acid ligands, it was demonstrated metal chelating polymer chain length and density may be manipulated to tailor both overall material iron chelating capacity (chain length) and ligand to metal binding ratio (chain density on food contact surface). Carboxylic acid functionalized PP (PP-g-PAA) enhanced the antimicrobial activity of lysozyme against Listeria monocytogenes under conditions that minimized protein fouling onto the charged food contact surface (PP-g-PAA, pKabulk 6.45). Compared to PP-g-PAA, hydroxamic acid functionalized PP (PP-g-PHA) was hypothesized to have a higher performance stability due to its low effective charge (pKabulk 9.65) and high specific affinity for iron. PP-g-PHA retained iron chelating capacity over a wide range of pH (3.0-5.0) and viscosity (~1 to 105 mPa·s) conditions as well as in presence of competing ions (Na+, Mg2+, Ca2+) and hydrocolloids typically found in foods. In order to investigate the efficacy of catechol based surface modifications, a metal chelating material inspired by polyphenol chemistry was developed. Polyphenol coatings were fabricated by oxidative polymerization of catechol and catechin from the surface of PP. Application of coating onto chitosan functionalized PP prevented coating delamination in food simulants under standard migration test conditions. Polyphenol coated PP exhibited both iron chelating and radical scavenging capacity for dual antioxidant functionality. In accelerated storage studies, polyphenol coated PP extended the lag phase of lipid oxidation and inhibited lycopene degradation in oil-in-water emulsions (pH 4.0). This work demonstrates the synthesis of non-migratory metal chelating active packaging materials and their antimicrobial and antioxidant applications. Such technology may allow for the removal of synthetic additives from product formulations, while maintaining food safety, quality, and shelf life

Political masculinities, crisis tendencies, and social transition: Toward an understanding of change

This introduction to the special issue on “Political Masculinities and Social Transition” rethinks the notion of “crisis in masculinity” and points to its weaknesses, such as cyclical patterns and chronicity. Rather than viewing key moments in history as points of rupture, we understand social change as encompassing ongoing transitions marked by a “fluid nature” (Montecinos 2017, 2). In line with this, the contributions examine how political masculinities are implicated within a wide range of social transitions, such as nation building after war, the founding of a new political party in response to an economic crisis, an “authoritarian relapse” of a democracy, attempts at changing society through terrorism, rapid industrialization as well as peace building in conflict areas. Building on Starck and Sauer’s definition of “political masculinities” we suggest applying the concept to instances in which power is explicitly either being (re)produced or challenged. We distinguish between political masculinities that are more readily identified as such (e.g., professional politicians) and less readily identified political masculinities (e.g., citizens), emphasizing how these interact with each other. We ask whether there is a discernible trajectory in the characteristics of political masculinities brought about by social transition that can be confirmed across cultures. The contributors’ findings indicate that these political masculinities can contribute to different kinds of change that either maintain the status quo, are progressive, retrogressive, or a mixture of these. Revolutionary transitions, it seems, often promote the adherence to traditional forms of political masculinity, whereas more reformatory transition leaves discursive spaces for argument

"Nested" cryptic diversity in a widespread marine ecosystem engineer: a challenge for detecting biological invasions

<p>Abstract</p> <p>Background</p> <p>Ecosystem engineers facilitate habitat formation and enhance biodiversity, but when they become invasive, they present a critical threat to native communities because they can drastically alter the receiving habitat. Management of such species thus needs to be a priority, but the poorly resolved taxonomy of many ecosystem engineers represents a major obstacle to correctly identifying them as being either native or introduced. We address this dilemma by studying the sea squirt <it>Pyura stolonifera</it>, an important ecosystem engineer that dominates coastal communities particularly in the southern hemisphere. Using DNA sequence data from four independently evolving loci, we aimed to determine levels of cryptic diversity, the invasive or native status of each regional population, and the most appropriate sampling design for identifying the geographic ranges of each evolutionary unit.</p> <p>Results</p> <p>Extensive sampling in Africa, Australasia and South America revealed the existence of "nested" levels of cryptic diversity, in which at least five distinct species can be further subdivided into smaller-scale genetic lineages. The ranges of several evolutionary units are limited by well-documented biogeographic disjunctions. Evidence for both cryptic native diversity and the existence of invasive populations allows us to considerably refine our view of the native versus introduced status of the evolutionary units within <it>Pyura stolonifera </it>in the different coastal communities they dominate.</p> <p>Conclusions</p> <p>This study illustrates the degree of taxonomic complexity that can exist within widespread species for which there is little taxonomic expertise, and it highlights the challenges involved in distinguishing between indigenous and introduced populations. The fact that multiple genetic lineages can be native to a single geographic region indicates that it is imperative to obtain samples from as many different habitat types and biotic zones as possible when attempting to identify the source region of a putative invader. "Nested" cryptic diversity, and the difficulties in correctly identifying invasive species that arise from it, represent a major challenge for managing biodiversity.</p

Design and baseline characteristics of the finerenone in reducing cardiovascular mortality and morbidity in diabetic kidney disease trial

Background: Among people with diabetes, those with kidney disease have exceptionally high rates of cardiovascular (CV) morbidity and mortality and progression of their underlying kidney disease. Finerenone is a novel, nonsteroidal, selective mineralocorticoid receptor antagonist that has shown to reduce albuminuria in type 2 diabetes (T2D) patients with chronic kidney disease (CKD) while revealing only a low risk of hyperkalemia. However, the effect of finerenone on CV and renal outcomes has not yet been investigated in long-term trials. Patients and Methods: The Finerenone in Reducing CV Mortality and Morbidity in Diabetic Kidney Disease (FIGARO-DKD) trial aims to assess the efficacy and safety of finerenone compared to placebo at reducing clinically important CV and renal outcomes in T2D patients with CKD. FIGARO-DKD is a randomized, double-blind, placebo-controlled, parallel-group, event-driven trial running in 47 countries with an expected duration of approximately 6 years. FIGARO-DKD randomized 7,437 patients with an estimated glomerular filtration rate >= 25 mL/min/1.73 m(2) and albuminuria (urinary albumin-to-creatinine ratio >= 30 to <= 5,000 mg/g). The study has at least 90% power to detect a 20% reduction in the risk of the primary outcome (overall two-sided significance level alpha = 0.05), the composite of time to first occurrence of CV death, nonfatal myocardial infarction, nonfatal stroke, or hospitalization for heart failure. Conclusions: FIGARO-DKD will determine whether an optimally treated cohort of T2D patients with CKD at high risk of CV and renal events will experience cardiorenal benefits with the addition of finerenone to their treatment regimen. Trial Registration: EudraCT number: 2015-000950-39; ClinicalTrials.gov identifier: NCT02545049

Fourier Transform Infrared Studies on the Dissociation Behavior of Metal-Chelating Polyelectrolyte Brushes

The dissociation behavior of surface-grafted polyelectrolytes is of interest for the development of stimuli-responsive materials. Metal-chelating polyelectrolyte brushes containing acrylic acid (PAA) or hydroxamic acid (PHA) chelating moieties were grafted from the surface of polypropylene (PP). Fourier transform infrared (FTIR) spectroscopy was used to determine the effective bulk p<i>K</i>_a of the polyelectrolyte brushes (p<i>K</i>_a^bulk) and to characterize metal-chelating behavior. The p<i>K</i>_a^bulk values of PP-<i>g</i>-PAA and PP-<i>g</i>-PHA were 6.45 and 9.65, respectively. Both PP-<i>g</i>-PAA and PP-<i>g</i>-PHA exhibited bridging bidentate and chelating bidentate iron chelation complexes. This is the first reported determination of the p<i>K</i>^a,bulk of surface-grafted poly­(hydroxamic) acid

Retaining Oxidative Stability of Emulsified Foods by Novel Nonmigratory Polyphenol Coated Active Packaging

Oxidation causes lipid rancidity, discoloration, and nutrient degradation that decrease shelf life of packaged foods. Synthetic additives are effective oxidation inhibitors, but are undesirable to consumers who prefer “clean” label products. The aim of this study was to improve oxidative stability of emulsified foods by a novel nonmigratory polyphenol coated active packaging. Polyphenol coatings were applied to chitosan functionalized polypropylene (PP) by laccase assisted polymerization of catechol and catechin. Polyphenol coated PP exhibited both metal chelating (39.3 ± 2.5 nmol Fe³⁺ cm^–2, pH 4.0) and radical scavenging (up to 52.9 ± 1.8 nmol Trolox eq cm^–2) capacity, resulting in <i>dual</i> antioxidant functionality to inhibit lipid oxidation and lycopene degradation in emulsions. Nonmigratory polyphenol coated PP inhibited ferric iron promoted degradation better than soluble chelators, potentially by partitioning iron from the emulsion droplet interface. This work demonstrates that polyphenol coatings can be designed for advanced material chemistry solutions in active food packaging